An apparatus for pumping and/or measuring flow comprises a plurality of flaps having a cross section of a round first edge and a crescent second edge extending therefrom, which flaps are disposed about an axis of rotation and supported by at least one flange rotatable about the axis of rotation, wherein each of the flaps is pivotable about a pivot axis passing through the center of the round edge thereof. The assembly of the flaps, which fold into a shape having a cross section with a generally circular periphery is disposed eccentrically in a cylindrical cavity in a rotating relationship about the axis of rotation, wherein an intake port is disposed through the wall of the first half of the cylindrical cavity and a discharge port is disposed through the second half of the cylindrical cavity. The retracting and extending motions of the flaps are guided by cam rollers following cam guide grooves included in a rotating member that is driven positively or frictionally by the rotating motion of the flap assembly, or by a rotatable ring limiting the extension of the flaps, which ring is driven frictionally by the rotating motion of the flap assembly.
There is a strong demand for a positive displacement pump providing a high volume flow with a medium pressure boost and a high volume flow positive displacement flowmeter with minimum pressure drop, wherein the positive displacement pump or flowmeter does not suffer from a high mechanical friction arising from moving elements under relative motions in rubbing relationships or from high fluid dynamic drag on the moving parts lacking streamlined geometry. A typical example of the applications of the positive displacement pump with a high flow rate and low friction loss is the super-charger for automobile engines as the state of the art in the automobile engine technology shows the advantage and preference of the super-charger over the turbo-charger. There are wide varieties of positive displacement flowmeters applied to all kinds of flow measurements in industry and commerce at the present time and, yet, most of these positive displacement flowmeters lack versatility because of the limitation thereof imposed by the high friction or low volume flow capacity inherent in these existing positive displacement flowmeters. The present invention teaches a positive displacement pump and/or flowmeter of a high volume flow capacity, that operates at a high efficiency as the energy loss due to friction on the moving elements in the pump or flowmeter is reduced to a minimum.